A range of halogenated alkenes are selective nephrotoxins, and some are nephrocarcinogenic, in rodent species. The bioactivation mechanism of haloalkenes includes hepatic glutathione S-conjugate formation, hydrolysis of the glutathione S-conjugates to the corresponding cysteine S-conjugates, transport of the cysteine S-conjugates to the kidney, and bioactivatioan by renal cysteine conjugate b-lyase. Most haloaklene-derived cystein S-conjugates are nephrotoxic in vivo and cytotoxic in vitro. In addition, chloroalkene- and bromine-containing, fluoroalkene-derived conjugates are mutagenic. The objective of our studies is to elucidate the detailed reaction mechanisms involved at the several steps in the pathway. Massspectrometry is used to help characterize conjugates and metabolites prepared by synthesis or derived from metabolism studies. Hence, the UCSF Mass Spectrometry Facility will help us in attaining our research goals by assisting in the elucidation of structures of conjugates and metabolites.